APOD: Diamonds in the Sky (2024 Apr 20)

Comments and questions about the APOD on the main view screen.
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APOD: Diamonds in the Sky (2024 Apr 20)

Post by APOD Robot » Sat Apr 20, 2024 4:07 am

Image Diamonds in the Sky

Explanation: When the dark shadow of the Moon raced across North America on April 8, sky watchers along the shadow's narrow central path were treated to a total solar eclipse. During the New Moon's shadow play diamonds glistened twice in the eclipse-darkened skies. The transient celestial jewels appeared immediately before and after the total eclipse phase. That's when the rays of a vanishing and then emerging sliver of solar disk are just visible behind the silhouetted Moon's edge, creating the appearance of a shiny diamond set in a dark ring. This dramatic timelapse composite from north-central Arkansas captures both diamond ring moments of this total solar eclipse. The diamond rings are separated by the ethereal beauty of the solar corona visible during totality.

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Re: APOD: Diamonds in the Sky (2024 Apr 20)

Post by johnnydeep » Sat Apr 20, 2024 3:43 pm

Alright, I'll ask: why aren't the two "diamonds" on the same line through the center of the eclipse? The centers of the Sun and Moon are coincident at totality, so why aren't the two diamond colinear with the center?
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Re: APOD: Diamonds in the Sky (2024 Apr 20)

Post by Chris Peterson » Sat Apr 20, 2024 3:50 pm

johnnydeep wrote: Sat Apr 20, 2024 3:43 pm Alright, I'll ask: why aren't the two "diamonds" on the same line through the center of the eclipse? The centers of the Sun and Moon are coincident at totality, so why aren't the two diamond colinear with the center?
The centers of the two bodies are only coincident at mid-totality if you're exactly on the center line of the shadow path.
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Re: APOD: Diamonds in the Sky (2024 Apr 20)

Post by johnnydeep » Sat Apr 20, 2024 6:13 pm

Chris Peterson wrote: Sat Apr 20, 2024 3:50 pm
johnnydeep wrote: Sat Apr 20, 2024 3:43 pm Alright, I'll ask: why aren't the two "diamonds" on the same line through the center of the eclipse? The centers of the Sun and Moon are coincident at totality, so why aren't the two diamond colinear with the center?
The centers of the two bodies are only coincident at mid-totality if you're exactly on the center line of the shadow path.
As usual with celestial mechanics, I don't get it. Is this not the apparent path of the Moon across the Sun that this composite was created from? :

april 8 2024 total eclipse path.jpg

EDIT: no, actually, if that was true, I'd expect to see both "diamonds" appearing on that line! So WTH is going on?
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Re: APOD: Diamonds in the Sky (2024 Apr 20)

Post by wrightdobbs » Sat Apr 20, 2024 6:19 pm

Hey there, I'm the author of this composite. These images were captured with my lens on a star tracker in Arkansas. The camera was not level at the time of the exposures because I didn't make any adjustments to the camera during tracking by adjusting where the camera was on the right ascension axis. The angle of the features is not meant to exactly match reality, but I did my best to not rotate any of the images when compositing them together, but some small adjustments were made. That might be why the alignment isn't exactly perfect. However, the goal of this image wasn't really attempting to get this composite astronomically correct, more just show the two diamond rings, roughly on opposite sides of the solar disc, combined with a HDR version of totality. Hope that helps clear some things up, Johnny. Additionally, the angle of the features in this composite are not meant to show the celestial bodies apparent motion through the sky, it's just what I thought was the better angle to not put any diamond rings smack in the middle of a coronal streamer.

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Re: APOD: Diamonds in the Sky (2024 Apr 20)

Post by johnnydeep » Sat Apr 20, 2024 7:20 pm

wrightdobbs wrote: Sat Apr 20, 2024 6:19 pm Hey there, I'm the author of this composite. These images were captured with my lens on a star tracker in Arkansas. The camera was not level at the time of the exposures because I didn't make any adjustments to the camera during tracking by adjusting where the camera was on the right ascension axis. The angle of the features is not meant to exactly match reality, but I did my best to not rotate any of the images when compositing them together, but some small adjustments were made. That might be why the alignment isn't exactly perfect. However, the goal of this image wasn't really attempting to get this composite astronomically correct, more just show the two diamond rings, roughly on opposite sides of the solar disc, combined with a HDR version of totality. Hope that helps clear some things up, Johnny. Additionally, the angle of the features in this composite are not meant to show the celestial bodies apparent motion through the sky, it's just what I thought was the better angle to not put any diamond rings smack in the middle of a coronal streamer.
Thanks for the further explanation, but I still don't understand why the two diamonds wouldn't be on the path of the Moon across the Sun, or at least close to it, allowing for a little tweaking. Not "exactly matching reality" is one thing, but this difference in the locations of the diamonds seem way more than not "exactly". What did it actually look like in reality for someone watching (or filming) at the time? [ Not that I still don't understand how Chris' reply above helps to explain my (apparent) misconception any better! ]
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Sa Ji Tario

Re: APOD: Diamonds in the Sky (2024 Apr 20)

Post by Sa Ji Tario » Sat Apr 20, 2024 11:17 pm

La Luna no pasa exactamente por el diámetro solar

Sa Ji Tario

Re: APOD: Diamonds in the Sky (2024 Apr 20)

Post by Sa Ji Tario » Sun Apr 21, 2024 3:37 am

The Moon does not pass exactly through the solar diameter.

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Re: APOD: Diamonds in the Sky (2024 Apr 20)

Post by Chris Peterson » Sun Apr 21, 2024 3:46 am

johnnydeep wrote: Sat Apr 20, 2024 7:20 pm
wrightdobbs wrote: Sat Apr 20, 2024 6:19 pm Hey there, I'm the author of this composite. These images were captured with my lens on a star tracker in Arkansas. The camera was not level at the time of the exposures because I didn't make any adjustments to the camera during tracking by adjusting where the camera was on the right ascension axis. The angle of the features is not meant to exactly match reality, but I did my best to not rotate any of the images when compositing them together, but some small adjustments were made. That might be why the alignment isn't exactly perfect. However, the goal of this image wasn't really attempting to get this composite astronomically correct, more just show the two diamond rings, roughly on opposite sides of the solar disc, combined with a HDR version of totality. Hope that helps clear some things up, Johnny. Additionally, the angle of the features in this composite are not meant to show the celestial bodies apparent motion through the sky, it's just what I thought was the better angle to not put any diamond rings smack in the middle of a coronal streamer.
Thanks for the further explanation, but I still don't understand why the two diamonds wouldn't be on the path of the Moon across the Sun, or at least close to it, allowing for a little tweaking. Not "exactly matching reality" is one thing, but this difference in the locations of the diamonds seem way more than not "exactly". What did it actually look like in reality for someone watching (or filming) at the time? [ Not that I still don't understand how Chris' reply above helps to explain my (apparent) misconception any better! ]
So I posted this animation on another thread, but I'll do it again because it's very relevant here. Note how much larger the Moon is than the Sun (which is why this was a long duration eclipse). Now I was only 100 meters from the center, so in this image the centers of the two bodies do cross. But imagine you were far off the centerline. The Moon and Sun would be offset, so the contact points wouldn't lie across a diameter. Now throw in the fact that the Moon isn't a circle, but has a jagged, mountainous edge, and maybe some field rotation... lots of things combine to explain why you might not see those contact points where you expect them.
_
prom_stack_anim2.gif
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Re: APOD: Diamonds in the Sky (2024 Apr 20)

Post by johnnydeep » Sun Apr 21, 2024 5:51 pm

Chris Peterson wrote: Sun Apr 21, 2024 3:46 am
johnnydeep wrote: Sat Apr 20, 2024 7:20 pm
wrightdobbs wrote: Sat Apr 20, 2024 6:19 pm Hey there, I'm the author of this composite. These images were captured with my lens on a star tracker in Arkansas. The camera was not level at the time of the exposures because I didn't make any adjustments to the camera during tracking by adjusting where the camera was on the right ascension axis. The angle of the features is not meant to exactly match reality, but I did my best to not rotate any of the images when compositing them together, but some small adjustments were made. That might be why the alignment isn't exactly perfect. However, the goal of this image wasn't really attempting to get this composite astronomically correct, more just show the two diamond rings, roughly on opposite sides of the solar disc, combined with a HDR version of totality. Hope that helps clear some things up, Johnny. Additionally, the angle of the features in this composite are not meant to show the celestial bodies apparent motion through the sky, it's just what I thought was the better angle to not put any diamond rings smack in the middle of a coronal streamer.
Thanks for the further explanation, but I still don't understand why the two diamonds wouldn't be on the path of the Moon across the Sun, or at least close to it, allowing for a little tweaking. Not "exactly matching reality" is one thing, but this difference in the locations of the diamonds seem way more than not "exactly". What did it actually look like in reality for someone watching (or filming) at the time? [ Not that I still don't understand how Chris' reply above helps to explain my (apparent) misconception any better! ]
So I posted this animation on another thread, but I'll do it again because it's very relevant here. Note how much larger the Moon is than the Sun (which is why this was a long duration eclipse). Now I was only 100 meters from the center, so in this image the centers of the two bodies do cross. But imagine you were far off the centerline. The Moon and Sun would be offset, so the contact points wouldn't lie across a diameter. Now throw in the fact that the Moon isn't a circle, but has a jagged, mountainous edge, and maybe some field rotation... lots of things combine to explain why you might not see those contact points where you expect them.
_
prom_stack_anim2.gif
Thanks. But to me that short clip looks like it should still show any "diamonds" on the travel path, and not (significantly) off it.

But here's a great - interactive! - animation of how the eclipse would look from Greers Ferry AK, which I think is where the APOD image author took it from. It's on the path of totality:

https://www.timeanddate.com/eclipse/in/ ... o=20240408

But I'll note that the path of the Moon is decidedly curved, which also surprised me. I still have a hard time visualizing these astronomical events, and the close those events are to Earth, the harder it seems to be!

And this animation also seems to show that any diamonds would be on symmetrically opposite sides of the Sun's (and Moon's) disk. True though, it is only an animation and not the real thing.
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Re: APOD: Diamonds in the Sky (2024 Apr 20)

Post by Rauf » Mon Apr 22, 2024 6:49 pm

It seems the link that is supposed to direct to yesterday's APOD instead redirects to the APOD for April 18.

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Re: APOD: Diamonds in the Sky (2024 Apr 20)

Post by johnnydeep » Mon Apr 22, 2024 6:55 pm

Rauf wrote: Mon Apr 22, 2024 6:49 pm It seems the link that is supposed to direct to yesterday's APOD instead redirects to the APOD for April 18.
That's usually remedied by refreshing (reloading) your browser page. Doing that almost always fixes any stale link issues that I sometimes see.
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Re: APOD: Diamonds in the Sky (2024 Apr 20)

Post by Rauf » Tue Apr 23, 2024 4:31 am

johnnydeep wrote: Mon Apr 22, 2024 6:55 pm
Rauf wrote: Mon Apr 22, 2024 6:49 pm It seems the link that is supposed to direct to yesterday's APOD instead redirects to the APOD for April 18.
That's usually remedied by refreshing (reloading) your browser page. Doing that almost always fixes any stale link issues that I sometimes see.
Not working. I don't think it's on my end.
zxc.jpg
This should send you 1 day back, not 2 days.
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Re: APOD: Diamonds in the Sky (2024 Apr 20)

Post by johnnydeep » Tue Apr 23, 2024 1:33 pm

Rauf wrote: Tue Apr 23, 2024 4:31 am
johnnydeep wrote: Mon Apr 22, 2024 6:55 pm
Rauf wrote: Mon Apr 22, 2024 6:49 pm It seems the link that is supposed to direct to yesterday's APOD instead redirects to the APOD for April 18.
That's usually remedied by refreshing (reloading) your browser page. Doing that almost always fixes any stale link issues that I sometimes see.
Not working. I don't think it's on my end.

zxc.jpg

This should send you 1 day back, not 2 days.
Ok, you’re right. I thought you were using the back button from within asterisk, but that works correctly. It’s the main APOD page that’s wrong. Web admins please take note!
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